Bright areas on Martian hillsides

On this image, wide expanses of Kieserite, a hydrated magnesium sulphate salt, can be seen. Hydrated implies that water molecules are incorporated into the crystalline structure. Kieserite produces the bright areas on the slopes of the western Candor Chasma, one of the largest canyons in the Valles Marineris on Mars. The Valles Marineris stretches for over 4000 kilometres from west to east along the Martian equator.